1. Field of Invention
The present invention relates generally to instruments for biometric identification, and more particularly, to a multimodal ocular imaging system used for biometric identification and methods for processing image data captured by the multimodal ocular imaging system.
2. Description of the Related Art
Due to the unique character of each individual's retina or iris, various systems attempt to use either the retina or the iris for biometric identification. Commercially available ocular imaging systems used for biometric identification generally use a single biometric modality. These imaging systems process images of the iris or the retina from only one of two eyes of a subject. None of these conventional systems processes images of both the iris and the retina in combination. Moreover, these systems do not process images from the iris and/or the retina from both eyes.
Conventional single-eye iris imaging systems suffer from several disadvantages. In particular, such systems may suffer from frequent failure to acquire an image, i.e. a high fail-to-acquire (FTA). The effectiveness of these iris imaging systems is often limited by occlusions caused by eyelids and eyelashes, lighting issues (controlled or uncontrolled), focus problems, pupil size variation (between different persons or with the same person), non-linear iris fiber distortion caused by expansion or contraction of the pupil, and rotation and skew of the head or eye. Such systems are also susceptible to spoofing. Moreover, auto focus functions of conventional iris-only systems are affected by scratches in eyeglasses or the reflections from eyeglasses. In fact, ANSI standards require enrollment to be without eyeglasses. Additionally, contact lenses can cause iris outer boundary segmentation problems. Moreover, colored contact lenses can result in spoofing.
Conventional single-eye retina imaging systems also have several disadvantages. For instance, problems with such retina imaging systems occur when visible light used for illumination blinds or distracts the user, when the user is not properly aligned with the image capture device, or when poor areas of the retina are chosen for imaging. Moreover, conventional retina-only systems are also negatively affected by focus problems as well as rotation and skew of the head or eye.
In addition, as a further disadvantage, the conventional imaging systems above process captured image data according to exhaustive edge detection, computationally expensive circle finding techniques, and other algorithms that are less appropriate for real time use and use on conventional processing devices.
While the iris systems described previously only process an iris image from only one of two eyes, there are other existing devices that acquire iris images from both eyes. However, such systems suffer from significant disadvantages. For example, these existing devices require a subject to walk up to a substantially stationary and device and look at a half mirror to position his eyes properly for image capture. Disadvantageously, this approach requires the subject to position himself so that his eyes are at the “right” height for image capture, or alternatively, the acquisition device must repositioned to accommodate the height of the subject, which may vary from 4 feet to 7 feet.